Experimental Study of Rainfall and Splashes Acting on the Surface of a Concrete Structure
Nagaoka University of Technology
Concrete Laboratory

INTRODUCTION
Concrete has an excellent structural performance anddurability, but is affected by early deterioration when is
subjected to a marine environment. The most common
cause of deterioration is corrosion of the reinforcementsteel, with a subsequent sapling of concrete. This
deterioration is caused by two agents, the rainwater, and thesalt that flies with the waves of the sea until reaching theconcrete structure. Once the salt and rainwater reach thesurface of the concrete structure, moisture and salt
infiltrates into the structure. The corrosion on the steel bars
is rotten and causes cracks in the concrete. However, theamount of moisture and sea salt are not the same in all thesurfaces of the structure. Therefore, it is necessary to know
certainty the distribution of moisture and sea salt. In orderto supply this problem, this research aims to study andevaluate the distribution of moisture and sea salt on thesurface of two different sections of vehicular bridge,
simulating the environment acting in this structure. Within
this environment, there is rainwater and sea salt that comeswith the waves, rainwater and sea salt that reach theconcrete surface, humidity and salt that runs through thestructure by gravity and finally, as time passes, theevaporation of water with the sun.
2EXPERIMENTAL METHOD
2.1 Whole Experimental Facilities
Fig. 1 shows the experimental facilities used in all theexperiments, composed for wind generator system, rainfall
generator system and two reinforcement concretespecimens.
2.2 Wind Reproduction
For the reproduction of the wind, a frame of ½ inch steel
tubes was constructed, measuring 140mm (length) ×100mm (width) × 2500mm (height) and divided every
500mm by wooden boards, such as it is shown in Fig.1.
The structure is made up of 12 fans, distributed 2 for eachtable. Each fan contains an electric power of 405 / 560W.
For wind speed measurement, 6 wind receiver fans wereused, each with its data logger. The receiving fans wereplaced in the middle of the base of Specimens A and B withthe help of metal arms, each with a height of 15mm, 50mm,100mm, 150mm, 200mm, and 250mm.
In each specimen the wind speed was measured at 6
different distances, 250mm, 500mm, 1000mm, 2000mm,3000mm and 4000mm, starting from the front of thespecimen as reference 0mm. In all cases the wind speed
was recorded for a period of 5 minutes.
2.3 Rainfall Reproduction
For the reproduction of the rain, 3 frames wereconstructed, of the same material and caliber as the frameof the fans. The measurements are 210mm (length) ×

LUIS ARTURO GARCIA MARTINEZ
Professor Takumi SHIMOMURA

1SpecimenRainfall
Generator
SystemWind
Generator
SystemFig. 1. Whole Experimental Facilities

Fig. 2. Specimens A and B Dimensions (mm)SpongeSea Salt
SplashPlastic

Fig. 3. Hydrophilic
SpongesFig. 4. Water Sensitive
Paper

Fig. 5. Surface Rainfall
Amount ExperimentFig. 6. Surface Splashes
Amount Experiment

2.5

3.5

2.5

2.0

3.7

2.0

3.8

1.5

3.5

1.5

2.2

1.0

2.4

0.5
0.00

3.3 Surface Splashes Amount
250

200

200

Height (cm)

250

150

100

150
100

50

5000 400 800 1200
0 400 800 1200
Rainfall Amount (ml/m2/min) Rainfall Amount (ml/m2/min)Fig. 9. Rainfall Amount vs. Fig. 10. Rainfall Amount vs.
Height (Specimen B)
Height (Specimen A)
0

Fig. 11. shows the surface splashes amount data ofSpecimen B, obtaining by the pixel counting. On the topstep, the highest moisture concentration was found at theheight of 135cm with 4.61 l/m2 and in the bottom step inthe height of 35cm with 7.59 l/m2. With these data, we cancorroborate that in this structure shape, there is an area
where the splashes did not reach the surface of the structure.

3.0

Height (m)Height (m)3.0

3.2 Surface Rainfall AmountIn this experiment, the amounts of rainfall wereobtained for each specimen, as we can see in Fig. 9 and Fig.
10. For a better understanding of the results, we divided inthree columns the hydrophilic sponges. The left row as blue,
the center row with red and the right row with green. If we
see the graph of specimen A, we see that at the top it was
the highest concentration of water and as it went down, theamount of water decreases. On the other hand, in specimen
B, we can see that it also shows in the upper part a greater
concentration of water. Also, under the step the water did
not reach the concrete surface. However, in the lower partof the structure it was observed that up to 45cm above, thewater could reach the structure.

Height (cm)700mm (width) × 3700mm (height), shown in Fig. 1. Fourcone nozzles were placed on top of each frame, which havethe function of simulating rain. The water was raised withthe help of pressure tanks, one tank per structure.
To measure the amount of rainfall, a plastic cylinderand hydrophilic sponges were used inside, as shown in Fig.
3. The distribution of the devices was as follows: on thefront of each specimen 33 of them and 3 more at the top,shown in Fig. 5.
Once the ventilation system and the rain generator were
switched on, the time in which the experiment was carriedout was 4 and a half minutes for both specimens.
2.4 Splashes Reproduction
For this experiment a special equipment was usedwhich throws tiny drops of water, simulating the drops ofwater and salt that reach the surface of the structure withthe air. The method used for conducting the experiment
was the use of the water sensitive papers, shown in Fig. 4.
The distribution of this papers was as follows: on the frontof each specimen 11 of them, as shown in Fig 6. Without
making use of the rain generator, the time during which theexperiment was conducted was approximately 2 to 3
seconds for both specimens.
2.5 Specimens Configuration
As specimens, 2 reinforcement concrete structures of asection of a full-scale vehicular bridge were used. Slabtype and T beam type bridge profiles were selected, towhich the specimen names A and B were attributed
respectively, as shown in Fig. 2.
3 EXPERIMENTAL RESULTS AND DISCUSSION
3.1 Wind Velocity
In this experiment, the speeds of 6 points with different
heights and at different distances from the front of thespecimen were obtained. The results shown in Fig. 7 andFig 8. are the results of the distance of 250mm. If we see
the two graphs, wind speeds vary depending on the shapeof the structure. Obtaining the maximum of the air velocity
as the low and high part of each specimen and in the center
the minimum values.

3.34.048

Wind Velocity (m/s)

4.6

Fig. 11. Surface Splashes Amount (l/m2/)

1.0

5.1

4 CONCLUSIONS

0.5

5.5
5.2

It was demonstrated that the adhesion amount of rainfall
and splash particles to the surface is affected by the shape ofthe structure and wind condition. In cases with wind, theadhesion amount of rainfall is greater than the no wind cases.
The adhesion amount of rainfall and splashes particles tosurface of the structures can be estimated by results. Finally,
it was possible to demonstrate that the adhesion amount ofrainfall and splashes is not the same in all places of theconcrete structure.

0.0048
Wind Velocity (m/s)

Fig. 7: Wind Velocity vs. Fig. 8: Wind Velocity vs.
Height (Specimen B)
Height (Specimen A)